In the known way, the cab suspension of telescopic-arm handling vehicles comprises three or four mounting points fitted with rubber mounts. These rubber mounts provide limited filtration of vibrations in the low frequencies, in high-magnitude shocks with an amplitude of the order to one decimeter.
Another suspension system used on agricultural tractors or all-terrain machines involves linear-travel spring-damper assemblies which have a degree of freedom in the direction of vertical translation. Such a suspension system does, however, entail stabilizing the other degrees of freedom through the use of link rods or parallelograms. However, the independence of the mounting points and the weight distribution allow disruptive coupling between the bouncing, pitching and rolling movements of the cab.
In order to avoid these undesirable movements, stabilizing torsion bars that limit the coupling may be provided. It is also possible to provide active systems comprising actuators and sensors driven by the on-board computer system of the machine comprising the cab.
Document FR 2 749 265 describes a main suspension with just one single U-shaped torsion bar to limit the connections between the chassis and the suspended bodyshell. The bar is secured by fixings at its base and by two rotational articulations at the respective ends of its arms. The reduction of noise bridges between the chassis and the driving cab of the vehicle means that the cab can be very well soundproofed at low cost. The use of the U-shaped torsion bar which constitutes one sole main suspension member thus means that the cost of suspending the cab can be reduced. However, in order to avoid pitching movements a U-shaped secondary torsion bar is provided, interposed between the cab and the chassis. This U-shaped secondary torsion bar is positioned in such a way that its base runs parallel to the axis of the vehicle and its arms run transversely to the said axis.